Novel Use of Surfactants in Copper Chemical Mechanical Polishing (CMP)
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Novel Use of Surfactants in Copper Chemical Mechanical Polishing (CMP) Youngki Hong1, Udaya B. Patri2, Suresh Ramakrishnan2, and S.V. Babu2, 3 1 Interdisciplinary Engineering Science, Clarkson University, Potsdam, New York 13699 2 Department of Chemical Engineering, Clarkson University, Potsdam, New York 13699 3 Center for Advanced Materials Processing, Clarkson University, Potsdam, New York 13699 ABSTRACT In this study, the interaction between several kinds of surfactants and copper surface was examined to control the dissolution of copper during CMP. Among those surfactants, sodium dodecylsulfate (SDS), one of the conventional anionic surfactants, showed effective interaction with copper and significantly suppressed the dissolution of the copper at acidic and neutral pH ranges in a model copper CMP slurry system consisting of 3 wt% fumed silica, 1 wt% glycine, and 5 wt% hydrogen peroxide in deionized water. The inhibition performance of copper dissolution by SDS is better than that of Benzotriazole (BTA), a conventional inhibiting agent of copper dissolution in a copper CMP slurry. INTRODUCTION Adsorption of surfactants at the solid-liquid interface has been studied and applied in many applications over the past 20 years [1]. In the field of microelectronic device fabrication, this concept has been mainly applied to the stabilization of particulate dispersions in wet cleaning and in CMP [2-9]. Spontaneous organized molecular assemblies on the surface of electronic materials, one of the concepts of self-assembled monolayers (SAMs), have widened the application of the adsorption of surfactants at the solid-liquid interface to other areas such as nano-patterning [10]. This concept of SAMs can also be applied to CMP, not for particulate stabilization but for the maximization of the topographical selectivity to increase planarization efficiency and optimize material removal selectivity [11, 12]. Surfactant layers that are adsorbed on a metal or a dielectric surface can act as inhibiting layers against unfavorable chemicaletching during CMP. Due to electrostatic interactions, these layers can also selectively cover heterogeneous material surfaces that are exposed during CMP and hence facilitate selective material removal. In this presentation, we show experimental data that are the results of our initial attempts to clarify the interaction of copper film and surfactants during CMP. Conventional ionic surfactants and a non-ionic surfactant have been investigated. The effect of these surfactants on copper CMP was studied in one of the typical copper CMP slurry systems, 1wt.% glycine and 5wt.% hydrogen peroxide in deionized water with 3wt.% fumed silica at different pHs. EXPERIMENTAL DETAILS Polishing experiments were carried out using a bench-top Struers DAP-V polisher using copper disks (99.999% purity) as polishing specimens. The polishing table (platen) was rotated at 90 rpm with an applied down force of 6.3 psi, while the copper disk was held stationary. Slurry was dispersed at a rate of approximately 60 ml/m
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